Observation of the $B_s^0 \to J/\psi K_s^0 K^\pm \pi^\mp$ decay

Abstract

Decays of the form B0 (s) → J/ψ K0 S h +h (′)− (h (′) = K, π) are searched for in protonproton collision data corresponding to an integrated luminosity of 1.0 fb−1 recorded with the LHCb detector. The first observation of the B0 s → J/ψ K0 SK±π ∓ decay is reported, with significance in excess of 10 standard deviations. The B0 → J/ψ K0 SK+K− decay is also observed for the first time. The branching fraction of B0 → J/ψ K0 S π +π − is determined, to significantly better precision than previous measurements, using B0 → J/ψ K0 S as a normalisation channel. Branching fractions and upper limits of the other B0 (s) → J/ψ K0 S h +h (′)− modes are determined relative to that of the B0 → J/ψ K0 S π +π − decay.